The present invention relates generally to a control device for essentially any illumination device or system comprising multiple ballasts and multiple lamps. More particularly, the present invention relates to a dimming apparatus for gas discharge or incandescent luminaires having multiple ballasts and lamps therein that enables selected ones of the ballasts and their associated lamps to control the illumination level of a specific area
Different tasks require various levels of illumination. For example, an office worker may desire brighter illumination over his desk than a computer operator would want over his computer console.
Dimming devices have been proposed to adjust the lumen level of light sources. For example, a wireless lighting control system can employ a radio frequency (RF) transmitter and receiver to adjust the illumination level of a light source(s) for a particular area. However, this type of RF control system has drawbacks. Specifically, the luminaires may not always receive the RF signaling from the transmitter, and so the lumen level may not be adjusted as desired. Accordingly, factors such as signal strength (e.g., the proximity of the transmitter to the receiver) becomes an issue for adjusting the illumination level. This can be a significant problem in a facility where the luminaires are suspended from the ceiling (e.g., on the order of thirty feet or more above the ground) and are difficult to reach for maintenance purposes. Many RF control systems employ sequential circuit operation and control signaling to benefit from the simplicity of only having to use one specific RF signal for the control command. Assuming a sequential control circuit is used, if one luminaire is unable to receive signals re-transmitted from the transmitter of another luminaire, and therefore does not extinguish or enable its lamps to adjust the lumen level as desired, that luminaire can become out of sequence with the other luminaires in the facility, causing improper lighting. To correct such a problem, all of the luminaires would have to be cycled off and then on, and the RF receiver(s) and transmitter(s) repositioned in order to obtain better reception within the RF control system of the luminaires. Accordingly, a need exists for a lighting control system that is hard-wired with respect to the luminaires and provides accurate and consistent lumen level adjustment within the operating area.
In addition, existing lighting control systems are disadvantageous because they generally employ sequencing through predetermined steps to power up and power down selected ones of a plurality of lamps. Some lamps are therefore subjected to shorter burn times than other lamps. For example, in a luminaire having eight lamps that are controlled by four two-lamp ballasts, the typical cycle is operate none of the lamps, two of the lamps, four of the lamps, six of the lamps, or all eight of the lamps, depending on how may signals are sent by the radio transmitter. When only two lamps are desired, the same two lamps are typically powered on, while the remaining lamps are powered down. Similarly, when only four or six of the lamps are desired, the same subsets of lamps are selected, while the remaining lamps are subjected to less burn time. Using fixtures wherein some lamps age more rapidly than others presents maintenance problems. A need therefore exists for a lighting control system that rotates use of each of the lamps in a multiple-ballast and multiple-lamp luminaire to more evenly distribute their burn times.
In accordance with the present invention, a lighting control system is provided to selectively operate ballasts in a multi-ballast, multi-lamp luminaire via relays to control the lumen output level of the luminaire.
In accordance with an aspect of the present invention, the lighting control system employs a sequential control device and signaling to operate selected numbers of the ballasts in a multi-ballast, multi-lamp luminaire.
In accordance with another aspect of the present invention, the luminaire is provided with a control input for receiving a control signal. The control signal can be generated via a wall-mounted switch or other device operable to generate an output signal. The number of ballasts operated by the luminaire increases or decreases sequentially in response to one of consecutive pulses, signal level transitions or interrupts in the control signal.
In accordance with another aspect of the present invention, the control device is hard-wired to the relays (e.g., a counter and decoder combination) to obviate the need for a programmable integrated circuit and allow for a more economical implementation.
In accordance with yet another aspect of the present invention, the control device is a programmable integrated circuit that provides for operation of selected numbers of the ballasts in response to a control signal. Different subsets of the ballasts can be selected to distribute the burn times of the lamps.
In accordance with still yet another aspect of the present invention, the lighting control system can arrange addressable luminaires in different zones and addresses for selected luminaires can be transmitted via the control signal. The programmable integrated circuit can also track actual burn times of luminaires and use this information to select which ballasts to operate.
In accordance with an embodiment of the present invention, a luminaire having a plurality of ballasts connected to a plurality of lamps is provided which further comprises: (1) a plurality of relays connected to respective ones of the plurality of ballasts; (2) a control device connected to each of the plurality of relays; and (3) a control input for providing a control signal to the control device. The control device comprises a counter for counting and generating an output signal in response to the control signal, and a decoder configured to receive the output signal and sequentially select which of the plurality of relays to actuate, thereby operating the corresponding ones of the plurality of ballasts in response to the output signal. The control signal is a DC signal comprising pulses. The counter is operable to increment the output signal in response to each pulse. The decoder is configured to implement a truth table whereby all of the plurality of ballasts are powered on in response to a first one of the pulses, and then one or more subsets of the plurality of ballasts are powered down in response to subsequent ones of the pulses until all of the plurality of ballasts are powered down.
In accordance with another embodiment of the present invention, the decoder is configured to implement a truth table whereby all of the plurality of ballasts are powered down in response to a first one of the pulses, and then one or more subsets of the plurality of ballasts are powered on in response to subsequent ones of the pulses until all of the plurality of ballasts are powered on.
In accordance with another embodiment of the present invention, a luminaire having a plurality of ballasts connected to a plurality of lamps is provided and further comprises: (1) a plurality of relays connected to respective ones of the plurality of ballasts; (2) a control device connected to each of the plurality of relays; and (3) a control input for providing a control signal to the control device. The control device comprises a programmable controller that is programmed to sequentially select which of the plurality of relays to actuate and thereby operate the corresponding ones of the plurality of ballasts in response to the control signal. The programmable controller is operable to select which of the plurality of ballasts to operate to distribute the burn times of the plurality of lamps.